The invention relates to an installation for heating a substance contained in receptacles by applying microwaves thereto, the installation comprising a microwave heater station having microwave application means, and a support suitable for supporting the receptacles in the heater station.
It is known from Patent Application PCT/FR01/02698 that, in order to ensure that a substance contained in receptacles is heated uniformly, it is advantageous to provide an end wall (the bottom or the lid) of each of the receptacles with an uninterrupted extra thickness of dielectric material, and to limit the extent to which microwaves pass through the side wall of each of the receptacles by providing said side wall with an electrically conductive material that reflects microwaves.
Heating by applying microwaves concerns domestic applications, for heating up or for defrosting (thawing) food. It also concerns industrial applications, in which microwaves are used for pasteurizing or sterilizing a substance, in particular food, contained in a receptacle.
The above-mentioned patent application proposes for the receptacle to be formed by a tray directly containing the substance to be heated by the microwaves. The receptacle can also be a utensil in which a tray containing such a substance can be disposed for heating said substance in a microwave oven, e.g. a domestic microwave oven. That patent application also proposes disposing a utensil of that type on the conveyor of a microwave heating installation, the utensil serving to receive trays containing a substance to be heated by applying microwaves thereto in that installation, in particular for pasteurizing and sterilizing the substance.
Such a known installation operates quite satisfactorily, but at a cost that is relatively high. A large number of utensils must be disposed on the conveyor in order for the installation to operate at an industrial rate of throughput.
Unfortunately, the cost of each utensil is relatively high. The extra thicknesses are disposed on the bottoms of the utensils, and the trays of substance that are to be disposed in those utensils must have their bottoms provided with cavities suitable for receiving said extra thicknesses.
The installation serves to pasteurize or sterilize the substance contained in the trays, but, prior to being consumed, said substance must generally be heated up again by the consumer in a domestic microwave oven. Since the trays must be shaped as indicated above in order to fit the specific shape of the utensils on the conveyor, it is difficult to provide the trays with means enabling the distribution of the microwaves to be made uniform during said heating in a domestic microwave oven.
Thus, with an installation of the type known from the prior art, the substance contained in the trays can be satisfactorily sterilized and pasteurized, but that generates a relatively large extra cost for the installation, and prevents the trays from offering the possibility of being heated uniformly in preparation for consumption of the substance, so that the consumer always finds zones that are cold or zones that are too hot in the substance contained in the trays.